costings depend on square footage and cubic footage. So not really relevant as a judge.
I have had projects using both types and some with heat recovery systems as well. These properties all have under floor heating which dose not require excessive heat.
All seem very happy customers with the results. I think that this is the way forward but would assume a secondary heating for the winter to give a boost would be good . wood burner etc
Just my views as not involved in the technical spec / fitting